The present invention relates to a method of continuously producing resinoid abrasive wheels for cutting hard metal materials, especially superhard metal materials such as stainless steel and special steel.
Generally, pores play an important role in resinoid abrasive wheels for cutting hard materials. When a hard metal material is cut by such a resinoid abrasive wheel, the pores in the wheel permit escape of particles of the cut material and reduce heat generation during the cutting operation. The presence of the pores further permits abrasion of the wheel, whereby refreshing the abrasive surface at all times so that the wheel retains a high cutting performance for a prolonged period of time. Accordingly, such effects are not achievable if the amount of the pores is less than is desired, whereas the presence of an excessive amount of pores will reduce the strength of the wheel. Thus the amount of pores is closely related to the cutting performance and strength of the abrasive wheel. It is therefore desired that a suitable amount of pores be present in the abrasive wheel in a well-balanced uniform distribution.
The present inventor has already proposed in U.S. Pat. No. 3,950,149 a method for continuously producing resinoid abrasive wheels comprising the steps of kneading abrasive grains and a binder together, molding the resulting composition into a block, heating the block by a high frequency heater, rolling the heated block into a sheet, blanking out circular pieces from the rolled sheet, and baking the circular pieces. With this method and other conventional methods, a foaming agent is used to form pores in the resinoid abrasive wheel. Stated more specifically, the foaming agent is admixed with the abrasive grains in a specified ratio in the kneading step, such that the foaming agent forms pores in the abrasive wheel on chemical reaction.
However, when chemically reacted, the foaming agent forms pores of varying sizes and shapes in the resulting abrasive mixture. Further when the uncured abrasive mixture is rolled on the opposite sides in the rolling step, not a few pores are broken down and disappear. For these reasons, it has heretofore been impossible to form within the resinoid wheel a sufficient amount of pores of uniform size and shape, with the resulting problem that the resinoid wheel produced by the convention methods is not fully satisfactory in curing performance.